Effects of small changes in Pao, on the ventilatory response to CO2 infusion

Environ. Exercise Physiol. S(5): 1426-1432, 1983.-The steady-state ventilatory responses to CO, inhalation and two levels of intravenous CO2 infusion were examined in chronic awake dogs. Responses were obtained for four treatments: 1) air breathing, in which arterial O2 tension (Pao,) increased during infusion; 2) normoxia, Pa o2 maintained at control levels; 3) hypoxia, Pao, = 70 Torr; and 4) hyperoxia, Pao, = 160 Torr. In three dogs, the ventilatory responses were obtained for treatments 1, 2, and 4 and in an additional three dogs for treatments 2, 3, and 4. Analysis of the data by directional statistics indicates that the response to infusion was hyper-capnic for all treatments, and the slope of the response (change in minute ventilation divided by change in arterial CO, tension) was identical to that of CO * inhalation. Also, the slopes of the responses for the low infusion rate, CO, output (VCO,) = 50%